Continuously variable resistor



Nov. 17, 1953 w. J. MAIRS 2,659,794

CONTINUOUSLY VARIABLE RESISTOR Filed Oct. 30, 1951 Patented Nov. 17, 1953 ooNrINUoUsLY VARIABLE Rasrsroa vwilliam J. Maira, Waltham, Ma., mmm to Technology Instrument Corporation, Acton,

Application October 30,1951, Serial N0. 253,815

The present invention relates to a continuously variable resistor, and more particularly to a variable resistor having characteristics of the slide wire potentiometer. i

The slide wire potentiometer provides a continuously variable resistor having particular utility in certain applications. A continuously variable resistor of this type is often times needed in a more compact form. and hence there have been provided helically'wound resistors having a contact which moves in a helical path to engage the resistance wire. Such arrangements, however, involve certain complex constructions in order to move the contact along the resistance wire without introducing an additional resistance factor due to improper contact with the wire. Such arrangements furthermore are limited to a linear relation between the movement of the actuating control and the resistance element.

In accordance with the present invention it is proposed to obviate certain disadvantages heretofore encountered in the construction of acompact continuously variable resistor of the potentiometer type by holding the contact stationary and moving the resistance wire or exible resistance element thereacross. Furthermore, an arrangement can be provided for a non-linear change of the contact with respect to the resistance wire for a uniform movement of the actuating control. l

Therefore, it is an object of the present invention to provide a new and improved compact continuously variable resistor of the potentiometer type.

Another object of the invention is to provide an improved compact continuously variable resistor wherein the adjustable wire contact is held stationary.

Other and further objects of the present invention subsequently will become apparent by reference to the present description taken in conjunction with the accompanying drawing wherein:

Figure 1 is a top view of a continuously variable resistor embodying the principles of the present invention;

Figure 2 is a rear view of the device shown in Figure 1;

Figure 3 is a cross sectional view of one portion of the device shown in Figure 1; and

Figure 4 is a top view of a device similar to 2 Claims. (Cl. 2 01-59) able bushing and having a locking collar Il at its end. The control shaft l2 carries a gear Il at the front of the supporting panel II which is engaged by two other gears I5 and I8 mounted on shafts I1 and I8.

reel 2| is mounted on the shaft I9. A flexible resistance element or wire 22 is wound in the grooves of the two insulated reels I9 and 2|.

. directly tothe shaft I8.

Figure 1 wherein a non-linear relationship is The resistance element or wire 22 is wound on to one of the reels and off from the other reel. The resistance element or wire 22 in moving from one reel to another engages an electric contact strip carried by a support rod 23.

The shafts I1 and I8 yare mounted in suitable bushings carried by the panel I I and held in position by lock nuts 25 and 26 respectively.

In order that the resistance element or wire 22 will be in proper contact with the stationary contact strip 24, the insulated reel I9 may have construction such as that' illustrated in detail in Figure 3. It will be noted that the reel I9 has an internal bore 28 which engages a vsleeve 29. The reel will be retained or locked in position on the sleeve 29 by a set screw 21 which also serves as an electric terminal for one end of the resistance element or wire 22.V The other end of the resistance element or wire 22 may be connected A helical spring 3|v interconnects the sleeve 29 with a collar '32 ailixed to the end of the shaft I9 by a suitable clamping screw 33 as may be seen for figure 32. The spring 33 is so arranged as to provide a biassing force between the shaft I1 and the reel I9 so that the resistance element or wire 22 is always subjected to a certain degree of tension. There is an arrangement provided for maintaining good electric contact between the stationary contact 24 and the resistance element or wire 22 irrespective to slight irregularities in manufacture of the two insulated reels I9 and 2| or any lost motion vand backlash between the gears I4, I5 and I6.

In the event that a non-linear relationship is desired between the movement of the control shaft and the movement of the wire across the stationary contact an arrangement similar to that shown in Figure 4 may be employed. A panel 35 carries on suitable shafts frusto-conical reels 36 and 31 on which grooves are provided for a flexible resistance element or wire which engages the stationary contact carried between support rod 38. Itis believed that it now will be apparent to those skilled in the art that other conngurations may be provided for the rotatable insula- 'rhe shaft n carries a groove insulated reel- I9 and a similar grooved tor members 36 and 37 so that a desired nonlinear relation can be obtained.

While for the purpose of illustrating and describing the invention a preferred embodiment has been shown in the drawing, it is to be understood that the invention is not to be limited thereby, since such variations are contemplated. as may be commensurate with the purpose and scope of the invention set forth in the accompanying claims.

I claim as my invention:

l. A continuously variable resistor comprising a vertical support panel, two shafts mounted perpendicular to one side of said panel, two insulated grooved non-cylindrical drums mounted on said shafts, one of said drums being fixed to its shaft, the other drum being mounted for rotation relative to its shaft, means for simultaneously rotat ing said shafts, a. resistance wire mounted in the grooves of said drums to be unwound on to the other, a sliding stationary Contact mounted between said drums parallel to the surfaces thereof and beyond a plane tangent to the surfaces of said drums, means for maintaining substantially constant contact between said sliding stationary contact and said wire comprising a helical spring interposed between the shaft and said latter drum tending to produce rotation of said drum relative to its support shaft.

2. A continuously variable resistor comprising a vertical support panel having mounted thereon two parallel rotatable shafts, two insulated grooved frusto-conical drums mounted on said shafts, one of said drums being fixed to its shaft, the other drum being mounted for limited rotation relative to its shaft, means for simultaneously rotating said shafts. a resistance wire mounted in the grooves of said drums to be unwound from one drum and wound on to the -other drum, a sliding stationary contact mounted be- References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 263,870 De Khotinsky Sept. 5, 1882 420,894 Thomson Feb. 4, 1890 1,213,723 Zeisel Jan. 23, 1917 1,977,291 Scofield Oct. 16, 1934 

